Lamberti G A, Feminella J W, Resh V H
Division of Entomology and Parasitology, University of California, 94720, Berkeley, CA, USA.
Oecologia. 1987 Aug;73(1):75-81. doi: 10.1007/BF00376980.
Field experiments were conducted to assess the effects of different population densities of the herbivorous caddisfly Helicopsyche borealis on periphyton biomass and on its own growth rate in Big Sulphur Creek, a third-order stream in northern California, USA. Stream enclosures were used to vary grazer density from one-eighth to twice natural density (1/8X-2X) in two experiments (35 d and 60 d), which spanned the period of most rapid larval growth. Periphyton biomass and chlorophyll a were inversely related to grazer density. Grazer densities of 1/8X-1/2X moderately reduced periphyton when compared to an ungrazed control, whereas densities of 1X-2X greatly depleted periphyton. The growth rate of H. borealis larvae declined with increasing larval density. Growth rate was highest at densities of 1/8X-1/2X; larvae grew more slowly at 1X and showed no growth at 2X. Weekly supplementation of periphyton to 1/4X, 1X, and 2X densities significantly increased the final body mass of larvae at 1X and 2X (by 26% and 50%, respectively, compared to unsupplemented larvae) but did not change the body mass of larvae at 1/4X. These results suggest that periphyton is a limiting resource in Big Sulphur Creek and that H. borealis larvae compete exploitatively for that resource. Intraspecific competition may be an important, but often overlooked, feature of many herbivore populations in streams.
在美国加利福尼亚州北部的一条三级溪流大硫磺溪中，进行了野外实验，以评估草食性毛翅目昆虫北方 Helicopsyche borealis 不同种群密度对附生植物生物量及其自身生长速率的影响。在两个实验（35天和60天）中，使用溪流围隔将食草动物密度从自然密度的八分之一变化到两倍（1/8X - 2X），这两个实验跨越了幼虫生长最快的时期。附生植物生物量和叶绿素a与食草动物密度呈负相关。与未放牧的对照相比，1/8X - 1/2X的食草动物密度适度降低了附生植物，而1X - 2X的密度则使附生植物大量减少。北方 Helicopsyche borealis 幼虫的生长速率随着幼虫密度的增加而下降。在1/8X - 1/2X的密度下生长速率最高；在1X时幼虫生长较慢，在2X时没有生长。每周向1/4X、1X和2X密度的幼虫补充附生植物，显著增加了1X和2X密度下幼虫的最终体重（与未补充的幼虫相比，分别增加了26%和50%），但没有改变1/4X密度下幼虫的体重。这些结果表明，附生植物是大硫磺溪中的一种限制资源，北方 Helicopsyche borealis 幼虫对该资源进行了竞争性利用。种内竞争可能是溪流中许多食草动物种群的一个重要但经常被忽视的特征。
